Telephone office alarm circuit



May 24, 1932. H. M. BASCOM TELEPHONE OFFICE ALARM CIRCUIT Filed July 7, 1951 fi m INVENTOR E .11. 306600100 BY z f 7%% ATTORNEY HENRY M. BASC'OM, OF BROOKLY N, NEW YORK,

Patented May 24, 1932 UNITED STATES P T FICE ASSIGNOR T0 AMERICAN rnnnrrionn AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TELEPHONE OFFICE ALARM CIRCUIT Application filed July 7, 1931. Serial No. 549,252.

This invention relates to telephone sys.

tems and more particularly to improvements in signaling arrangements at central ofiices associated with the lines of such systems.

The signaling arrangements of the invention are particularly adapted for use in cen tral ofiices of the common battery manual type in which the subscribers line lamp is connected in series with the subscribers line and hence,operated without the use of individual line relays. One of the primary objects of the invention consists in providing for central oflice equipment of this type an alarm circuit common to a plurality of lines and suitable for giving an indication whenever any of'the line lamps are operated. r.

The arrangements of the invention would be particularly suitableffor night alarm purposes.

Arrangements heretofore provided for giving a night alarm at central oiiices of the above type have comprised a common relay inserted in series with the line lamps.

, Where the line lamps are connected directly -to the lines such arrangements may not be desirable because the cumulative effect of the leakage currents on a large number of lines might cause false operation of the common relay and the alarm controlled thereby when the lines were not in use. In the arrangements of the invention, any tendency for false operation of the alarm due to excessive leakage current is eliminated by connecting a cold cathode discharge tube, such 'as a neon lamp, between each line and they common relay controlling the alarm. A separatebattery will also be provided to operate the relay and the discharge tubes as hereinafter pointed out. Other objects and features of the invention will appear more fully from the detailed description thereof, hereinafter given.

The invention may be more fully understood from the following description, together with the accompanying the figure of which is shown a circuit diagram embodying a preferred form of the invention.

In the drawing are shown a plurality of telephone lines L L and L interconnectdrawing in ing subscribers stations with central-office equipment. "The subscribers station jcon-' nected to lineL wo 'uld comprise the 'usuaII equipment such as theringer; 1, induction coil 2, receiver *3,'andutransmitter 4s. The

stations connectedto lines Lg'and L -would comprise similar equipment; The elines would terminate at (the central office inthe jacks J ,J andJ m At these. jacks the tip sides of the lineswould be' extended to signaling equipment and the ring'sides of the lines would be grounded as-shown at 5, 6-

and 7. -An'-operators 'cord terminating in the plug P mightbe provided for establish: ing connections'with the lines. Connected-V in serieswith each line at the central'oflice would be the subscribers linelampsI8, 15' and 17K These would common. central ofiice battery-:QL =.The relay: 11 and battery 12, which is common: to all of be fconnected to the the lines,'is.providecl at the central office for" controllingjan alarm device 13.- A! cold cathode discharge tube, such as. the neon lamps 10, 14, and 16, is provided, connected between each line and the common alarm relay 11. v 7

Thearrangements of the invention operate in the'following manner: :The regular line lamp 8 forms a shunt around the neon lamplO, the relay 11, and the alarm battery 12, and serves to prevent the breakdown of the'neon lamp '10 untilthe' line L isclosed by the subscriber." During the time the line L is idle, leakage current flows from the central office battery 9.-through the line lamp 8' to leakage ground and produces a potential dropacross the line lamp, 8.3 This drop is negligible and, when added to the voltage of the alarm battery 12,the total voltage will not be enough to break down the neon la mp10. It is pointed out that without this shunt the total voltage of the central office battery 9 and, alarm battery '12 would berapplied across the neon lamp, 10 to leakage ground' and might cause false operation v of thearrangements. 1

When the line L is closed bythe subscriber] originating a call, the leakage path to ground is shunted by the loop resistance at "theline a common battery at said lamps connected in series guished. This oflice battery 9. The increased current produces an increased potential across the lamp 8 which is of suflicient magnitude so that when added to the voltage of the alarm battery 12 it will break down the neon lamp 10. The internal resistance of the neon lamp is greatly reduced after break-down and passes through current to operate a common relay 11 which in turn will operate the alarm device 13.. i

When the operator answers, by inserting her cord circuit into the jack J the circuit through which the line lamp 8 is operated is opened at the jack J Thecircuitconditions are then changed so that the line lamp 8 and the neon lamp 10 are in series with the alarm battery 12 only. The resultingvoltage across the neon lamp 10 under these conditions will be so low that the lamp 10 will be extinwill cause the common relay 11 to release and stop the alarm.

The operation of the signaling arrangements with respect to other lines such as the lines L and L is similar to that heretofore described. The line lamps such as 8, 15, and 17, might each be replaced by an equivalent resistance such as'that shown in dotted lines at 20. Under these conditions the neon lamps might be used to indicate the calling line without changing the. operation of the above arrangements.

While the invention has been disclosed as embodied in certain specific forms which are deemed desirable, it is understood that it is capable of: embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is: 1

1. A telephone system comprising a plurality of subscribers telephone lines terminating at a central office, subscribers line lamps connected in series with each line to office, and an alarm relay at said ofiice common to all of said lines, said relay being connected through an auxiliary battery to said common battery and through individual cold cathode discharge tubes to each of said lines. V

2. A telephone system comprising a plu-- rality of subscribers telephone lines terminating at a central office, subscribers line with eachline to a common battery at said office, and an alarm relay at said 'office common to all of said lines, said relay being connected through an auxiliary battery to said common battery" and throughindividual gas filled discharge lamps to each of said lines, the voltage'of said auxiliary battery alone being insufficient to break down or maintain said discharge lamps in operation.

3. A telephone system comprising a plurality of subscribers telephone lines terminating at a central office, subscribers line 'cuit including another iliary battery lamps connected one in series with each of said lines to a common battery at said central ofiice, a circuit connected in parallel with one of said subscribers line lamps, said circuit including a discharge tube and an alarm relay and an auxiliary battery, and another circuit in parallel with another of said subscribers line lamps, said last mentioned cirdischarge tube and said alarm relay and said auxiliary battery.

4. A telephone system comprising a plurality of subscribers telephone lines terminating at a central oflice, a plurality of resistance elements connected one in series with each of said lines to a common battery at said central 05306, and an alarm relay at said centraloiiice common to all of said lines, said relay being connected through an auxthrough individual discharge tubes to each or" said lines, the voltage of said auxiliarybattery alone being insuiiicient to break down or maintain said discharge tubes in operation and the voltagedrop across each of said resistance elements due to leakage currents from said common battery to ground being insuflicient when added to the voltage of said auxiliary battery to break down or maintain said discharge tubes in operation.

In testimony whereof, I have signed my name to this specification this 6th day of July,.1931. 1

r HENRY M. BASCOM.

to said common battery andv 

